CHAIN TRANSMISSION SYSTEM

Abstract: The invention relates to a chain transmission system which comprises several form pieces (1) and a wheel arrangement further comprising a drive wheel (7) for transmitting the chain of form pieces (1). The bearing surface (1b) of the chain comprises openings (2) formed by a pressure edge (X), a bottom (Y) and a trailing edge (Z) and arranged near the point of articulation, across the running direction and eccentrically in relation to the joint division. The openings (2) of the chain are in cooperation with contact surfaces (9), such as sprockets (9a), being part of the drive wheel (7).

Description: Chain transmission system The invention relates to a chain transmission system comprising several form pieces connected with each other by points of articulation, and a wheel arrange¬ ment comprising at least one drive wheel for trans¬ mission of the chain of said form pieces. The bearing surface of the chain comprises preferably at least one opening formed by a pressure edge, a bottom and a trailing edge and arranged near the point of articula¬ tion, across the running direction and eccentrically in relation to the joint division..Upon transmission of the chain, the openings of the chain are in co- operation with contact surfaces, such as sprockets or the like, being part of the drive wheel and arranged according to the openings, transversely to the running direction of the chain, the free contact width of the contact surfaces, such as the length of the sprockets, corresponding preferably to that of the form pieces. During cooperation started by contact of the contact surface and the pressure-edge side of the opening, the chain being at least bending over the drive wheel, the width of the forming contact area corresponds preferably to the width of the form piece, after which cooperation, during straightening of the chain, the contact surface escapes from the opening at the trailing-edge side. At least in a chain that is sub¬ stantially straight, the free inner diameter of each opening in the longitudinal direction is substantially greater than the contact length of the contact surface, such as the diameter of the sprocket. A chain structure partly of the above-mentioned type is previously known e.g. from the publication FI-64707 disclosing a form piece comprising an opening that is transverse to the running direction of the chain, has a length corresponding to the width of the form piece, and is advantageously placed near the second articulation point of the form piece. Thus when the chain bends over the drive wheel, an advantageous lever arm is formed, thanks to which the chain force effective on the chain structure presses said openings more firmly towards the sprockets of the drive wheel. This solution reduces so-called jumping to a con¬ siderable extent. Further, thanks to the lever arms formed, the chain structure is easily released from the drive wheel, thus preventing so-called captivating. U.S. Patent 4,123,947 discloses a conventional chain structure manufactured of a non-metallic material. In this kind of a solution, transmission from the drive wheel to the chain structure is usually carried out by a drive wheel with a standardized tooth system. A chain structure according to the publication FI-64707 has proved to be good in practice. In certain uses, such as in water purification plants, however, plastic or corresponding non-metallic materials for the chain structures have been resorted to for reducing corrosion and the specific weight of the chain. Thus, due to high loads as well as the more flexible behaviour of the new materials in comparison with steel, said jumping has occurred, whereby the chain on the drive wheel, because of slight elongation or vibration of the chain or for another reason, rises from the sprockets of the drive wheel so that the drive wheel starts to rotate as its sprockets glide freely along the outer surface of the chain. Thus, for restarting the original transmission of the chain and the drive wheel, the rotation of the drive wheel is stopped and the chain is placed over it again. In practice, the damage caused by such jumping can be very significant and call for a variety of service, maintenance and other measures. The cooperation of a conventional chain structure according to U.S. Patent 4,123,947 and a drive wheel used in connection therewith is most advantageously based on applying a standardized evolvent curve on the tooth system of the drive wheel. In practice, the teeth on the drive wheel of a chain structure according to the U.S. patent correspond in their basic profile to the basic profiles of the pressure and trailing edges of the opening applied in the above-mentioned Finnish publication. In practice, the chain structure according to the publication FI-64707 is, thanks to the lever arms, more advantageous than the solution according to said U.S. publication. However, neither publication presents a solution for preventing said .jumping by increasing the dept of the basic profile, because as a result, the chain could not be released on the return side of the drive wheel so-called captivation would occur. For eliminating the problems presented above, the publication FI-85755 presents a more developed solu¬ tion. In this publication, the improvement presented is based on the fact that during contact of the opening and the sprockets of the drive wheel, the free dimen¬ sion of the opening in the longitudinal direction of the chain is substantially greater than the correspond¬ ing measurement of the respective sprocket. The contact of said parts thus takes place between the sprocket and the pressure edge of the opening in the chain. Further, the greatest distance of the pressure edge from the central line of the form piece substantially exceeds the corresponding distance of the trailing edge. By this solution, it is possible to determine the height of the pressure edge of the form piece according to the application e.g. to a sharper angle than the evolvent profile, whereby jumping of the chain can be prevented. This solution is particularly suitable for applications where the chain runs con¬ stantly in the same direction. In spite of this, the chain can also be driven in a direction opposite to that for the main use, in which case the load, however, must be substantially smaller than that for the main use in order to prevent jumping. In connection with the change of direction, there is naturally also a delay, because the sprockets of the drive wheel glide along the bottom of the opening towards the trailing edge before the actual movement of the chain is started. The purpose of the chain transmission system of this invention is to provide a decisive improvement to the above-presented disadvantages and thus to improve the state of prior art substantially. For achieving this aim, the chain transmission system of the invention is primarily characterized in that the free inner diameter of the openings of the chain in the longi¬ tudinal direction is arranged to be changeable, wherein the openings of the chain of form pieces being at least in cooperation with the contact surfaces of the drive wheel, the free inner diameter of each opening in the longitudinal direction is at least partly changeable to be equal to the contact length of the corresponding contact surface, such as the diameter of the sprocket. The most important advantages of the chain transmission system of the invention are simplicity and reliability, whereby all the above-mentioned problems, such as jumping and captivating, can be avoided. Further, the chain according to the invention can be used with equal loading in both running directions. Thus no delay will be induced by a change in the running direction of the chain, but the chain will be im¬ mediately moved after a change in the direction. A form piece according to the invention can also be constructed so that the contact surfaces of the drive wheel are locked in the openings of the chain so that jumping becomes impossible in practice. Advantageous embodiments of the chain transmission system according to the invention will be presented in the other dependent claims on the chain trans¬ mission system. In the following description, the invention will be illustrated in detail with reference to the appended drawings, in which Fig. 1 shows the operating principle of an advantageous transmission system according to the invention in side view, and Figs. 2a and 2b show an advantageous form piece according to the invention in side view and in front view. According to the principle shown in Fig. 1, the chain transmission system comprises several form pieces 1 connected with each other at articulation points and a wheel arrangement which comprises further at least one drive wheel 7 for transferring the chain of said form pieces 1. The bearing surface lb of the chain comprises at least one opening 2 formed by a pressure edge X, a bottom Y and a trailing edge Z and arranged near the point of articulation, across the running direction and eccentrically in relation to the joint division. Upon transmission of the chain, the open¬ ings 2 of the chain are in cooperation with contact surfaces 9, such as sprockets 9a, being part of the drive wheel 7 and arranged according to the open- ings 2, transversely to the running direction of the chain. The free contact width of the contact sur¬ faces 9, i.e. the length of the sprockets 9a, cor¬ responds preferably to the width 1 of the form pieces. During cooperation started by contact of the contact surface 9 and the pressure-edge X side of the open¬ ing 2, the chain being at least bending over the drive wheel 7, the width of the forming contact area corresponds preferably to the width 1 of the form piece. After said cooperation, during straightening of the chain, the contact surface 9 escapes from the trailing-edge Z side of the opening 2. At least in a chain that is substantially straight, the free inner diameter e of each opening 2 in the longitudinal direction is substantially greater than the contact length of the contact surface 9, i.e. in the presented embodiment the diameter of the sprocket 9a. The free inner diameter e of the openings 2 in the chain in the longitudinal direction is arranged to be changeable, whereby the openings 2 of the chain formed by form pieces 1 being at least in cooperation with the contact surfaces 9 of the drive wheel 7, the free inner diameter e 1 of each opening 2 in the longitudinal direction is at least partly changeable to be equal to the contact length of the corresponding contact surface 9, i.e. the diameter of the sprocket 9a. As shown in Fig. 2b, each form piece 1 has two points of articulation 4, 5, of which the first one is ar¬ ranged as a solid projection 4 substantially narrower than the width 1 of the form piece and the second one as a fork 5. Further, each point of articulation 4, 5 is advantageously provided with a hole 6 with equal size, whereby for formation of the chain, each point of articulation can be formed by placing said projec¬ tion 4 of the previous form piece between the fork 5 of the next form piece and by placing a joint pin or the like in said holes 6. With particular reference to Fig. 1, the inner diameter e of the openings 2 in the longitudinal direction of the chain formed by form pieces 1 is arranged to be changeable upon revolution of successive form pieces 1 in relation to each other at joints 4, 5 to be at least partly smaller e" than the contact length of the contact surfaces 9, at least when the chain is fully bent over the drive wheel 7. Hence, as an advantageous embodiment particularly according to Figs. 1 and 2a, in the chain of form pieces 1 the pressure edge X of each opening 2 is arranged in the first form piece and the trailing edge Z in the second form piece as seen in the running direction of the chain, whereby the bottom Y of the opening 2 is arranged at least partly in the area of the joint 4, 5. Thus the form piece 1 comprises, as shown e.g. in Fig. 2a, a pressure edge X at its second point of articulation 5 and a trailing edge Z at its first point of articulation 4, respectively. In an advantageous embodiment, the form piece 1 shown in Fig. 2a is formed symmetrical in relation to its central point K, whereby the pressure edge X and trailing edge Z arranged in the points of articula¬ tion 4, 5 of the form piece 1 are substantially identical in form. The bottoms Y of the opening 2 at the points of ar- ticulation 4, 5 of the form piece 1 are connected to the pressure edge X and trailing edge Z in the form piece by a radius corresponding substantially to the form of the contact surfaces 9, such as the curvature of the sprocket 9a. In an advantageous embodiment, the bottoms Y of the opening 2 in the form piece 1 are further arranged parallel to the central line s connecting the holes 6 of the form piece 1. Further in an advantageous embodiment, the pressure edge X and trailing edge Z at the points of articula¬ tion 4, 5 in the form piece 1 are arranged to be partly straight, whereby as gliding a contact as possible is achieved between the sprockets 9a of the drive wheel and said pressure and trailing edges X, Z. According to the embodiment shown in Fig. 2a, the bearing surface lb of each form piece 1 is arranged to be at least partly hollow, such as in a form corresponding to the radius r3 of curvature of the drive wheel 7. Thus the pressure edge X and trailing edge Z at the first and second point of articulation 4, 5 are arranged to join the bearing surface lb of the form piece 1 in a rounded v way. In this way, a form piece with a curved form in all parts as seen in side view as well as a chain is obtained, whereby point¬ like loads on the wheel arrangement are eliminated. Furthermore, thanks to the rounded edges, the chain will not tend to carry e.g. material or impurities coming into contact with it in an unintended way. It is obvious that the invention is not limited to the embodiments presented above but it can be modified even to a great extent within the limits of the basic idea defined in the appended claims. The parts of the chain transmission system of the invention, such as the drive wheel and the form pieces, can naturally be manufactured of a variety of materials, such as plastics, metals, composite materials, ceramic mate¬ rials and/or the like, by using a variety of methods.

Claims: Claims : 1. Chain transmission system comprising several form pieces (1) connected with each other by points of articulation and a wheel arrangement comprising at least one drive wheel (7) for transmitting the chain formed by said form pieces, the bearing surface of the chain comprising preferably at least one open¬ ing (2) formed by a pressure edge (X), a bottom (Y) and a trailing edge (Z) and arranged near the point of articulation, across the running direction and ec¬ centrically in relation to the joint division, wherein upon transmission of the chain, the openings (2) of the chain are in cooperation with contact surfaces (9) , such as sprockets (9a) or the like, being part of the drive wheel (7) and arranged according to the open¬ ings (2) , transversely to the running direction of the chain, the free contact width of the contact surfaces, such as the length of the sprockets (9a) , corresponding preferably to the width (1) of the form pieces, wherein during cooperation started by contact of the contact surface (9) and the pressure-edge (X) side of the opening (2) , the chain being at least bending over the drive wheel (7) , the width of the forming contact area corresponding preferably to the width of the form piece (1) , after which cooperation, during straightening of the chain, the contact sur¬ face (9) escapes from the trailing-edge (Z) side of the opening (2) , at least in a chain that is sub- stantially straight, the free inner diameter (e) of each opening (2) in the longitudinal direction being substantially greater than the contact length of the contact surface (9) , such as the diameter of the sprocket (9a) , characterized in that the free inner diameter (e) of the openings (2) of the chain in the longitudinal direction is arranged to be changeable, wherein the openings (2) of the chain of form pieces (1) being at least in cooperation with the contact surfaces (9) of the drive wheel (7) , the free inner diameter (e 1 ) of each opening (2) in the longitudinal direction is at least partly changeable to be equal to the contact length of the corresponding contact surface (9) , such as the diameter of the sprocket (9a) . 2. Chain transmission system according to claim 1, wherein for formation of said chain, each form piece (1) has two points of articulation (4, 5), of which the first one is arranged as a solid projec¬ tion (4) substantially narrower than the width (1) of the form piece and the second one as a fork (5) , wherein each point of articulation (4, 5) is advanta¬ geously provided with a hole (6) with equal size, wherein for formation of the chain, each point of articulation can be formed by placing said projec¬ tion (4) of the previous form piece between the fork (5) of the next form piece and by placing a joint means, such as a joint pin or the like, in said holes (6) , characterized in that the inner dia¬ meter (e) of the openings (2) in the longitudinal direction of the chain of form pieces (1) is arranged to be changed upon revolution of successive form pieces (1) in relation to each other at joints (4, 5) to be at least partly smaller (e") than the contact length of the contact surfaces (9) , at least when the chain is fully bent over the drive wheel (7) . 3. Chain transmission system according to claim 1 or 2, characterized in that in the chain of form pieces (1) , the pressure edge (X) of each opening (2) is arranged in the first form piece and the trailing edge (Z) in the second form piece as seen in the running direction of the chain, wherein the bottom (Y) of the opening (2) is arranged at least partly in the area of the joint (4, 5). 4. Chain transmission system according to any of the claims 1 to 3 above, characterized in that the form piece (1) comprises a pressure edge (X) at least at its first or second point of articulation (4, 5) and a trailing edge (Z) at least at its second or first point of articulation (5, 4), respectively. 5. Chain transmission system according to claim 4, characterized in that the form piece (1) is formed symmetrically in relation to its central point (K) as seen in side view, wherein the pressure edge (X) and trailing edge (Z) arranged at the points of articula¬ tion (4, 5) of the form piece (1) are substantially identical in form. 6. Chain transmission system according to any of the claims 1 to 5 above, characterized in that the bottom (Y) of the opening (2) towards at least one point of articulation (4, 5) of the form piece (1) is connected to the pressure edge (X) and/or trailing edge (Z) in the form piece (1) by a radius correspond¬ ing substantially to the form of the contact sur¬ faces (9) , such as the curvature of the sprocket (9a) . 7. Chain transmission system according to claim 6, characterized in that the bottom (Y) of the open¬ ing (2) at least at one point of articulation (4, 5) in the form piece (1) is arranged to be at least partly straight and parallel to the central line (s) connecting the holes (6) of the form piece (1) . 8. Chain transmission system according to any of the claims 4 to 7 above, characterized in that the pressure edge (X) and/or the trailing edge (Z) at least at one point of articulation (4, 5) of the form piece (1) is arranged to be at least partly straight. 9. Chain transmission system according to any of the claims 1 to 8 above, wherein preferably the bearing surface (lb) of each form piece (1) is arranged to be at least partly concave, such as in a form correspond- ing to the radius (r3) of curvature of the drive wheel (7) , characterized in that the pressure edge (X) and trailing edge (Z) preferably at the first and second point of articulation (4, 5) are arranged to join the bearing surface (lb) of the form piece (l) in a rounded (v) way.

Inventors: TUOMIKOSKI PEKKA, TUOMIKOSKI, PEKKA
Applicants: FINNCHAIN OY, TUOMIKOSKI PEKKA, TUOMIKOSKI, PEKKA
Application year: 1994
Main classification: F16G13
IPC codes: F16G13, F16H7